I have a problem installing printers via the https://servername/ipp page. Usually, if our techs need to install a printer on some workstation, they launch the browser as administrator, click on a printer, get prompted for their eDirectory username/password and can install the printer successfully.

The problem occurs if the workstation is joined to DSfW domain. In such case, if I launch the browser as LOCALPC\Admin (a local account in Administrators group), I get the message "Printer ipp://servername/printername failed to install. The specified username is invalid". iPrint does not prompt for username/password.
If I launch the browser as a member of Domain Administrators group I can install the printer, but I don't like the idea of making all technicians Domain Administrators just so they can occasionally install a printer (we generally use iPrint Client Management).